One to two million people in the United States, suffer from type 1 diabetes mellitus. Diabetic cardiomyopathy is an impairment of heart muscle that exists independently of coronary artery disease, and is associated with diabetes mellitus. Diabetic cardiomyopathy is characterized by contractile dysfunction which contributes to myocardial infarction and heart failure. Hyperglycemia associated with diabetes mellitus, increases reactive oxygen species (ROS) generation. Because the mitochondrion is the primary site for ROS generation, determination of how mitochondria are affected by diabetes mellitus is crucial for understanding the pathogenesis. Examination of mitochondria is complicated by the fact that two mitochondrial subpopulations are present in the cardiomyocyte, interfibrillar mitochondria (IFM), which situate between the contractile apparatus and subsarcolemmal mitochondria (SSM) that exist beneath the plasma membrane. Currently, it is unclear how spatially distinct mitochondrial subpopulations are effected by diabetes mellitus making it difficult to ascertain their specific contribution to diabetic cardiomyopathy. Our long-term goal is to elucidate the mechanisms involved in the pathogenesis of diabetic cardiomyopathy as a prerequisite to the development of therapeutics designed to lessen cardiac complications associated with diabetes mellitus. The central hypothesis of this application is that cardiac IFM are at greater risk from diabetic insult than SSM. The objectives of this application are to determine the effect of diabetic insult on spatially distinct mitochondrial subpopulations, identify key factors that contribute to dysfunction in specific mitochondrial subpopulations, and to develop therapeutics that target spatially distinct mitochondria subsets.